I see a tilt down on a pretty high-contrast horizontally-striped canopy at that point, and I wouldn't be surprised if it's giving your camera fits. To confirm, you can check the shot in a viewer outside of premiere or AE.

I think it's a result of the codec in which the video camera recorded the shot. It's pretty easy to fake the tilt down with a few carefully-shot stills stitched together, using AE to simulate the tilt.